218 



SELECTION AND USE 



show best against a dark ground, while others are most easily 

 seen against a light one. Those who use the self-centering 

 turn-tables may readily centre their slides by painting on them 

 a ring of some water-color, which is easily washed off. The 

 ring is, of course, laid on the side opposite to that which 

 receives the object. 



MOUNTING NEEDLES. These are similar to dissecting needles, 

 but being used in balsam, varnish and similar substances, they 

 cannot be used for dissection, and should be kept by them- 

 selves. They are most easily cleaned by being warmed over the 

 lamp, and wiped with a piece of soft leather. When t be balsam 

 is burned on them, as recommended by some, it leaves a crust 

 which is not easily removed. 



COVER FORCEPS. In placing the cover on the object, the 

 ordinary forceps are very inconvenient. We 

 have long used a pair of forceps bent as in 

 Fig. 70, and with the points carefully 

 adjusted. The mode of using the instrument 

 will be obvious from the engraving. A very 

 ingenious device intended to answer the same 

 purpose has been invented by Dr. Fletcher. 

 These forceps are self-closing, so that the 

 thin glass cover is held without any effort. 

 After the cover is in position on the slide, 

 by pressing on the blades they open and allow it to slip out. 

 If the cover should 

 stick to the forceps 

 in the slightest de- 

 gree, it may be pre- 

 vented from moving 

 when the forceps 

 are removed by in- Fig. 71. 



sorting a common 



pin in the slit seen in Fig. 71. When using the forceps 

 shown in Fig. 70, the same end may be attained by means of a 

 wire fork (a hair-pin is as good as anything), which may be 

 made to straddle the nose of the instrument. 



Fig. 70. 



